Lead-free cartridge component and cartridge comprising same

ABSTRACT

An offensive charge intended for the manufacture of a cartridge for firing with a firearm does not contain lead. It is made of multiple projectiles ( 10 ), in which the projectiles are formed of at least two substantially spherical pellets ( 5 ) connected to one another by a metal connecting wire ( 6 ) of fixed predetermined length, the pellets being made of an alloy containing tin and antimony. A cartridge containing such projectiles, and a method for the mass-production of these lead-free projectiles are also described.

The present invention belongs to the field of ammunition used in hunting or firearms, and more particularly that of cartridges whereof the offensive charge consists of multiple projectiles of the birdshot type.

It relates to an offensive charge made up of multiple projectiles formed by pellets mechanically connected to one another by a wire, which does not include lead. Another aim of the invention is a cartridge for hunting incorporating such projectiles. A method for the mass production of these lead-free projectiles is also claimed.

When hunting small game such as ducks, the aim is to stop and quickly kill the animal in motion. In this case, one uses smooth-bore weapons to fire multiple non-profiled projectiles so as to increase the likelihood of a hit, while limiting the range of the projectiles so as to protect the people and property located in the firing direction.

It is known that hunting cartridges are made up of several components that perform different functions. The casing of the cartridge (cartridge case), which is generally cylindrical, contains a propulsive charge (powder) at one end and an offensive charge (birdshot or lead), separated by a wad. The wad performs two different functions: it retains the gases produced by the explosion and it exerts pressure on the birdshot by pushing it in an orderly manner outside the barrel of the gun. A traditional hunting cartridge contains from 30 g to 35 g or 36 g of projectiles, called lead shot, or 200 to 300 lead beads with a small diameter generally between 1 mm and 4 mm, in particular between 1.25 mm and 4 mm. The cartridges are distinguished from much larger buckshot, which refers to cartridges comprising fewer than 28 projectiles having a diameter from 5.65 mm to 8.65 mm, and which is prohibited for hunting in most French departments.

It is furthermore known, in particular from document U.S. Pat. No. 3,085,510, to use, as offensive charge for a cartridge, a set of at least two lead pellets connected to one another by a cord, preferably a single-filament wire like those used in fishing, so as to improve the kinetic properties of the projectile thus formed.

For some time, lead shot has been used as a projectile in hunting and shooting cartridges to increase the likelihood of hitting a small, moving target. More broadly speaking, heavy metals (metals with a high density) have been used in most ammunition to improve the kinetic characteristics of the projectiles. However, all of these materials are toxic, in particular lead, to which 1% to 8% arsenic, which is also toxic, is generally added. This toxicity is reflected at several levels: during manufacturing accidents; through the cumulative pollution on manufacturing sites that are responsible for lead poisoning; during their use, direct health problems related to the emission of lead vapors; and upon the destruction of unused ammunition.

That is why, since the 1980s, many countries have prohibited or reduced the use of lead in hunting cartridges in favor of less toxic cartridges that are said to be non-toxic. This first applies to waterfowl hunting in wet and phreatic zones.

An effort has been made to replace lead projectiles with other materials. First, steel shot was proposed. However, although steel has the advantage of being inexpensive, it is harder than lead (and may be considered non-deformable in terms of the stresses of interest to us). This hardness is problematic in terms of strength of the barrel of the guns. Indeed, with a hard material, the shot load forms a packed and resistant whole that causes burring of the surface of the connecting cone between the chamber of the rifle receiving the cartridge case and the barrel. Deterioration of the barrel is also observed through swelling or even explosion. Steel is also light (its density is comprised between 7.3 and 8.0, as opposed to 11.35 for pure lead), which imparts a significantly lower kinetic energy with an equal propulsive charge.

A metal such as tungsten, which is heavier than steel, is much more expensive (approximately ten times more), which disqualifies it from mass production. Although the use of bismuth is not explicitly prohibited, it should be avoided, since it is even more toxic than lead.

It has also been proposed by the prior art, in particular illustrated by document WO 93/22089, to have projectiles formed by pellets made from alloys of metal compounds making it possible to reduce the toxicity compared with lead pellets by associating a metal compound with a high melting point with a metal compound having a low melting point, such as tungsten and tin, respectively. These alloys are further formed so as to obtain projectiles with a density comparable to that of lead, in order to reproduce the kinetic properties of lead projectiles.

We can assert that to date no satisfactory solution has been found to produce nontoxic multi-projectile cartridges having characteristics as interesting as those of lead and having performance levels equivalent to those of lead projectiles in terms of range, perforating power and deformation with energy release.

Thus, according to one aim of the present invention, ammunition is sought for waterfowl hunting, i.e., a cartridge with no lead according to the laws applicable to wet zones. Another aim of the invention is to define a component for cartridges, i.e., a projectile with no lead and nevertheless having properties comparable to those of traditional lead projectiles. The present invention meets this need by proposing a multiple projectile for a firearm, and more particularly for smooth-bore weapons corresponding fully to these specifications. In particular, this aim is achieved owing to the choice of a composition of very specific metals to manufacture the pellets of the projectile, with a mechanical bond of several pellets to one another.

Still another aim of the invention is to have a method for the mass production of such projectiles that is economically acceptable.

At the origin of the invention, the present inventor noted that the key point for reproducing the performance levels of lead-based projectiles is not, as suggested by the prior art, seeking to come as close as possible to the density of lead through the alloys used, but rather to favor an alloy having a hardness close to that of lead. The issue of the difference in density may be settled by the number of pellets connected by a same wire, such a determination falling within the skills of one skilled in the art. It has thus been noted by the present invention that reproducing the hardness of lead takes priority in conditioning the obtainment of alloyed projectiles suitable for reproducing the performance of lead projectiles.

Thus, the present invention now proposes an offensive charge intended for the manufacture of a cartridge for shooting with a firearm, made up of multiple projectiles formed by pellets formed from at least two substantially spherical pellets connected to one another by a metal connecting wire with a fixed predetermined length, the pellets having a base of tin, which does not have a known toxicity for the environment. However, tin being very malleable (or even pasty), and having a lower hardness than that of lead, it cannot be used alone. To obtain a hardness close to that of lead, it is possible to use a tin alloy with another compound. The second component of the alloy of the pellets will be chosen from among those that are non-toxic and miscible with tin at least in certain proportions, which will be combined with the tin to obtain an alloy comparable to a soft metal, i.e., having a hardness equivalent to that of lead or a composition containing more than 80% lead. The choice fell on antimony, to obtain small, non-toxic metal pellets with an appropriate hardness.

In one embodiment of the offensive charge according to the invention, the alloy of the pellets is at least 99% made up of tin and antimony. All of the proportions will be given below in mass content.

According to one advantageous feature of the invention, the alloy of the pellets preferably comprises 90% to 98% tin and/or 2% to 10% antimony.

Preferably, a composition will be used including about 5% antimony and about 95% tin.

The projectiles according to the invention advantageously have characteristics as interesting as the traditional lead projectiles in terms of hardness on the one hand, such that crushing of the projectile on the target releases a large quantity of the energy that was given to it by the explosive charge of the cartridge, and in terms of mass on the other hand, this last feature being ensured by the fact that, although the density of the alloy according to the invention is lower than that of lead, the pellets are connected to one another within the projectile. Thus, the density of the tin is approximately 7.3, that of the antimony is 6.7, the density of this alloy meeting the above features is approximately 7.25 to 7.29. Such an alloy will also be significantly lighter than lead with an identical volume. This low density therefore appears insufficient to obtain a penetrating power (and therefore an effective range) similar to that of lead pellets. To resolve this drawback, several pellets are connected to one another, so as to form small clusters with a greater mass.

However, putting this idea into practice still had to overcome a certain number of obstacles: although it is known to connect buckshot pellets by piercing them, then threading them on a lead wire and binding the whole by twisting the wire, this method cannot be implemented for small pellets, for both technical and economic reasons.

The technical manufacturing difficulties resulting from the small diameter of the projectiles used for waterfowl hunting have been overcome. A method has been developed, which is part of the present invention, and allows the manufacture of clusters of small pellets of a non-toxic alloy with a base of tin and antimony connected by a metal wire that is also non-toxic.

As previously stated, according to a first aspect, the invention thus relates to an offensive charge intended to manufacture a cartridge for shooting with a firearm, made up of multiple projectiles, these projectiles being formed by at least two substantially spherical pellets connected to one another by a metal wire with a fixed predetermined length, said pellets being made from an alloy comprising tin and antimony. The pellets (or birdshot) are approximately spherical, as are the traditional lead hunting pellets. The connecting wire is also metal. It is strong enough to withstand the tensions and twisting occurring during the filling and packaging of the cartridges.

The pellets are joined in clusters of two, three or four, or even more, using a metal wire. One thus obtains projectiles of two or several secured pellets, the linear momentum of which at a given speed is a multiple of the linear momentum that the pellets would have considered alone. The number of impacts is reduced, but the kinematic properties are higher performing, such that the shooting is more effective. It has been observed that, for a projectile with two linked pellets, for example, one will have a doubled effective shooting distance with respect to a charge of non-linked pellets of the same alloy.

If the cartridge is filled with beads made from a tin-antimony alloy as recommended by the present invention, one will have a lower mass than with the same volume of lead beads. For example, for a volume of lead beads of 36 grams, one will have an identical volume of alloyed pellets weighing approximately 24 grams total, but whereof each projectile is one and one-half times heavier than the lead beads. Lastly, in this example, the effective shooting distance will be multiplied by 1.5. One has thus offset the low density of the tin and antimony by linking the pellets to one another.

The pellets, which preferably contain at least 99% tin and antimony, can also for example contain at most 1% (by mass) of a component other than tin and antimony. In the offensive charge according to the invention, the alloy of the pellets may for example further comprise no more than 1% of a third metal, excluding lead or another toxic metal, of course. This does not significantly alter the properties of the tin-antimony alloy. The main interest of this embodiment lies in reducing the raw material costs without affecting the desired qualities of the offensive charge.

According to one particularly preferred embodiment of the invention, the alloy of the pellets is made up of 94.5% tin, 5% antimony and 0.5% copper. This ternary alloy offers an ideal compromise in terms of kinematic properties of the projectiles and costs.

The length of the wire separating (and joining) two adjacent pellets is defined in advance during the manufacture of the pellet clusters. The pellets are further associated with the wire such that the distance separating them remains fixed after their manufacture, during the placement in the cartridge and during shooting. The association mode may be physical (for example, by pinching the wire in a notch formed in the pellet), but will preferably be chemical (by fusing the wire and the pellet), as will be seen in more detail later.

According to another advantageous feature of the invention, the connecting wire between two pellets is a brass wire, with a length comprised between 0.5 mm and 10 mm. The brass, which is an alloy of zinc and copper, is chosen from among those without lead. The brass connecting wire will contribute to the density of the projectile. It is flexible enough not to break under the effect of the acceleration during shooting and robust enough to withstand the passage in the known boxing machines. The length of the wire between two pellets is such that the pellets form a relatively compact projectile, and are close enough to avoid elastic return phenomena of the sling type.

According to the invention, the projectile preferably comprises two pellets with a diameter smaller than or equal to 4 mm connected to one another. This configuration makes it possible to offset the relatively low density of the tin. The assembly in twos optimizes both the mechanical and kinematic properties and the number of impacts obtained from firing a cartridge.

The projectiles as defined above are particularly suitable for waterfowl hunting, but also for any other type of game, where cartridges adapted to smooth-bore weapons are used. That is why the present invention also relates to a cartridge for shooting with a firearm, comprising a cartridge case in which a propulsive charge and an offensive charge are found separated by a wad, in which cartridge that offensive charge is made up of projectiles according to the preceding description. These cartridges can indifferently comprise a wad grease or a wad skirt.

A cartridge according to the invention preferably contains between 50 and 200 projectiles, formed by pellets connected in pairs. It is advantageously possible to use projectiles including pellets having a diameter comprised between 2.5 mm and 4 mm, for example 50 projectiles, in the form of 100 pellets with a diameter of 3.5 mm, connected in pairs. It will be recalled that a traditional cartridge from 30 to 35 g or 36 g contains 200 to 300 toxic lead beads, and that a buckshot cartridge comprises fewer than 30, typically 9, 12 or 15.

The invention also relates to a method for manufacturing projectiles intended to constitute the offensive charge of a cartridge, said projectiles being formed from at least two substantially spherical pellets connected to one another by a metal wire with a fixed predetermined length, said pellets being made from an alloy comprising tin and antimony. The method essentially comprises the following steps:

-   -   obtaining a machine comprising i) a furnace provided with a         reservoir able to contain said molten alloy, ii) a horizontal         plate mounted on a central rotation axis able to receive and         rotate a polymer matrix, and iii) means bringing said alloy from         the reservoir to a central upper orifice of said matrix;     -   producing a polymer matrix comprising two separable molds, i.e.,         an upper one including a central orifice, and a lower one,         between which an array of branched channels is arranged         extending along a substantially radial orientation from said         central upper orifice and each ending with a spherical cavity;     -   forming, in one of the molds, notches joining adjacent cavities,         taken at least in pairs;     -   installing a metal wire traversing said cavities and being         inserted in said notches;     -   assembling the molds to form the matrix, placing it on the         plate, and rotating the assembly;     -   pouring the molten alloy from the reservoir into the matrix         through the central orifice, while keeping said matrix rotating         such that the alloy penetrates the array of channels until it         reaches the spherical cavities through the effect of the         centrifugal force;     -   separating the mold and recovering the clusters of substantially         spherical pellets connected to one another by a wire.

All that remains is then to split the clusters of linked pellets into projectiles of at least two pellets, unless it has been provided from the beginning to insert wire segments only connecting the desired number of pellets into the notches.

The furnace may be of a known type, like those which have already been used to manufacture isolated lead beads (for example fishing sinkers), but without implementing the matrix according to the invention. The step of pouring with centrifugation lasts several tens of seconds, for example 20 seconds.

According to the inventive manufacturing method, the spherical cavities that are arranged in a matrix preferably have a diameter smaller than 4 mm.

Also preferably, in the manufacturing method according to the invention, the adjacent cavities between which notches are formed are arranged at a distance from one another comprised between 0.5 mm and 10 mm.

According to one feature of the manufacturing method according to the invention, the connecting wire is made from metal or a metal alloy having a melting temperature higher than that of the tin and antimony alloy, the latter being approximately 290° C. (as opposed to 450° C. for lead). Brass melts at around 800° C. As a result, the brass wire will be embedded and frozen in the tin- and antimony-based alloys during the molding, to form an assembly of pellets at a predetermined fixed distance.

The present invention will be better understood, and details relative thereto will appear, using the description provided below of one of its alternative embodiments, relative to the appended figures, in which:

FIG. 1 is a sectional view of a cartridge with a grease wad according to the invention.

FIG. 2 is a sectional view of a cartridge with a skirt wad according to the invention.

FIG. 3 is a diagrammatic illustration of a machine for carrying out the projectile manufacturing method according to the invention.

FIG. 1 shows a cartridge for shooting with a firearm, comprising the cartridge case 1, the butt 21 of which here is placed at the bottom. In the cartridge case 1 is a propulsive charge 2 and an offensive charge 3, which are separated by a grease wad 4 and a sealing member 44. The propulsive charge 2, in the lower part of the cartridge (partially hidden by the butt), is traditionally powder.

Another cartridge according to the invention, shown in FIG. 2, is a cartridge with a skirt wad 4. The skirt forms a well 41 having a curved base and ending with a shock absorbing element 42.

These two structures are of a known type. They contain the offensive charge 3, i.e., multiple projectiles 10 (as opposed to a bullet, which is a single projectile). Each projectile 10 comprises at least two pellets 5 connected by a wire 6.

In a first example, the pellets 5 are beads with a diameter of 3.5 mm, formed by an alloy of tin (94.5%), antimony (5%) and copper (0.5%). The connecting wire 6 that joins them is made from brass (lead-free quality). It maintains the pellets 6 in pairs, separated by a fixed distance of 7.5 mm, which form the projectiles 10. An offensive charge may be formed by 50 of these projectiles 10.

In a second example, the pellets 5 are pellets with a diameter of 2.5 mm, formed by an alloy of tin (95%) and antimony (5%). The connecting wire 6 made from brass (with no lead) the pellets 6 three by three, separated by a fixed distance of 6 mm. It is possible to produce an offensive charge comprising around one hundred of these projectiles 10, or 300 pellets.

The projectiles can be manufactured as follows, in reference to FIG. 3. A machine is used comprising a furnace 100 provided with a reservoir 110 able to contain the selected alloy. The device also includes a horizontal plate (not shown) mounted on a central rotation axis able to receive and rotate a polymer matrix. The matrix assumes the form of two separable molds, an upper one (not shown) and a lower one 11. An array of branched channels 13 is arranged between the molds. The upper mold is provided with a central upper orifice that is placed overhanging a nozzle supplied by means designed to bring the molten alloy from the reservoir 110, and to deliver a quantity of alloy into the central upper orifice of the matrix.

The branched channels 13 extend along a radial orientation from the center 12 of the molds and each end with a spherical cavity 14, having a predefined diameter smaller than 4 mm. Notches 15 joining adjacent cavities 13 are formed in one of the molds. The adjacent cavities 14 between which notches 15 are formed are placed at the desired distance from one another, comprised between 0.5 mm and 10 mm.

Next, the following process is used. The reservoir 110 of the oven 100 is filled with the compounds forming the desired alloy and is heated to reach the melting temperature of the alloy (i.e., 290° C. for a 90%-5% tin-antimony alloy). The lower mold 11 is placed on the plate of the device. Brass wires 6 are installed such that they traverse several cavities 14, by inserting them in the notches 15 to keep them in place. The matrix is closed by the upper mold and the plate is set in rotation. A quantity of alloy is poured through the central orifice of the matrix. The rotation is continued for around twenty seconds. It is left to cool for several minutes before removing the upper mold, then recovering the clusters of pellets connected by a metal wire.

All that remains is to separate the clusters into projectiles 10 with the desired length (number of pellets 5) and to place them in a tub of a boxing machine. 

1. An offensive charge intended to manufacture a cartridge for shooting with a firearm made up of multiple projectiles (10) formed by at least two substantially spherical pellets (5) connected to one another by a metal connecting wire (6) with a fixed predetermined length, wherein said pellets are made from an alloy comprising tin and antimony.
 2. The offensive charge according to claim 1, wherein the alloy of the pellets (5) is 99% made up of tin and antimony.
 3. The offensive charge according to claim 1, wherein the alloy of the pellets (5) comprises from 90% to 98% tin.
 4. The offensive charge according to claim 1, wherein the alloy of the pellets (5) comprises from 2% to 10% antimony.
 5. The offensive charge according to claim 1, wherein the alloy of the pellets (5) further comprises no more than 1% of a third metal.
 6. The offensive charge according to claim 1, wherein the alloy (5) is made up of 94.5% tin, 5% antimony and 0.5% copper.
 7. The offensive charge according to claim 1, wherein the connecting wire (6) between two pellets (5) is a brass wire with a length comprised between 0.5 mm and 10 mm.
 8. The offensive charge according to claim 1, wherein the projectile (10) comprises two connected pellets (5) with a diameter smaller than or equal to 4 mm.
 9. A cartridge for shooting with a firearm, comprising a cartridge case (1) in which a propulsive charge (2) and an offensive charge (3) are found separated by a wad (4), wherein said offensive charge is according to claim
 1. 10. The cartridge according to claim 9, wherein the offensive charge contains between 50 and 200 projectiles (10), formed by pellets (5) connected in pairs.
 11. A method for manufacturing an offensive charge according to claim 1, which comprises the following steps: pouring the alloy containing tin and antimony into a polymer matrix, comprising two separable molds, i.e., an upper one including a central orifice and a lower one (11), between which an array of branched channels (13) is arranged extending along a substantially radial orientation from said central upper orifice and each ending with a spherical cavity (14), separating the molds and recovering the clusters of substantially spherical pellets connected to one another by a wire (6).
 12. The manufacturing method according to claim 11, wherein the spherical cavities (14) of the matrix have a diameter smaller than or equal to 4 mm.
 13. The manufacturing method according to claim 11, wherein the adjacent cavities between which notches (15) are formed are arranged at a distance from one another comprised between 0.5 mm and 10 mm.
 14. The offensive charge according to claim 2, wherein the alloy of the pellets (5) comprises from 90% to 98% tin.
 15. The offensive charge according to claim 2, wherein the alloy of the pellets (5) comprises from 2% to 10% antimony.
 16. The offensive charge according to claim 3, wherein the alloy of the pellets (5) comprises from 2% to 10% antimony.
 17. The manufacturing method according to claim 12, wherein the adjacent cavities between which notches (15) are formed are arranged at a distance from one another comprised between 0.5 mm and 10 mm. 